Receiving apparatus for train control systems



R. K. CROOKS July 4, 1944.

' REQEIVING APPARATUS.FO R TRAIN CONTROL SYSTEMS 55 Y I E2212 M4 14 Filed Febflz, 1945 2 Sheets-Sheet 1 Ylrymmezmb 02251 C A MG [7 v 552 la' lb INVENTOR' [ZalplzfiCroo/am.

QL W ATTORNEY July 4, 1944.

Volzir' V Valli! R. K. CROOKS RECEIVING APPARATUS FOR TRAIN CONTROL SYSTEMS Filed Feb. 12, 1943 2 Sheets-Sheet A .V lzagemdaeedm ecew n Time - VOllagefnduo azhRoecben MMMM HIS ATTORNEY the train in inductive relation to the rails.

Patented July 4, 1944 UNITED STATES rATENToFFlcE .RECEIVING APPARATUS FOR TRAIN I CONTROL SYSTEMS f Ralph K. Crooks, Clearfield, Pa.,-assignor to The Union Switch and Signal Company, Swissvale,

Pa., a corporation of Pennsylvania Application February 12, 1943, Serial No. 475,628

4 Claims.

My invention relates to receiving apparatus for train control systems, and more particularly to such apparatus responsive to alternating current.

Systems using train carried train control apparatus responsive to alternating current are well-known. The alternating current is supplied to a track circuit which includes the track rails and energy is transferred from the track circuit to a train carried receiver mounted on In some systems the current is non-coded and in other systems it is coded by being periodically interrupted at a given code rate. In systems coded current, either the presence of non-coded current or the absence of current results in the most restrictive indication. The receiver ordinarily includes two inductors mounted on the train with one inductor over each rail, and the twoinductors connected in an additive manner. The electromotive force thus induced in the indoctors is or the same frequency as the rail current and in coded systems it is also of a code corresponding to the code of the rail current This received electromotive force is used to govem a master relay which in turn governs the train controlling device, and because the received electromotive force is of a relatively low energy level an amplifier is interposed between the receiver and the master relay. The receiver is connected to the input side of the amplifier through a filter which is tuned to resonance at the frequency of the alternating current to improve the operation and to suppress energy of frequencies other than that used by the train control system.

Shock excitation of the inductors due to propulsion current, extraneous magnetic fields and other conditions may occur. The nature of such shock excitation is such that a very high peak electromotive force may be induced in the inductors. This shock electromotive force may be at a greater or a lesser period than that of the alternating track circuit current, but when .its high peak vcltage'is impressed upon the inbe released to cause. a restrictive indication, and in code systems each such shock excitation may cause an adverse operation of the master relay which in code systems is a code following relay.

Accordingly, a feature of my invention is the provision of train control receiving apparatus incorporating novel means to reduce and minimize the oscillatory condition created. by shock excitation.

Again, a-feature of my invention is the provision of train control receiving apparatus incorporating novel means to avoid operation of the master relay due to shock excitation'of the receiving inductor.

Other objects, features and advantages of my invention will appear as the specification progresses. v

The features, objects'and advantages embodyingmy'invention I attain by providing a special control device which is incorporated in the receiving apparatus ahead of-the filter to reduce and absorb the energy induced in the inductors due to shock excitation to such a low value that the oscillatory condition in the resonant circuits created by such energy is not suflicient to cause an operation of the associated master relay. This control device includes two asymmetric units and means to negatively bias each such asymmetric unit by avoltage slightly greater than the peak value of the normal-control elece tromotive force picked up by the inductors. This control-deVice-is connected tothe input .circuit'ahead-of the' filter to shunt the relatively high peak value of the electromotive force created-by shock excitation before such electrometive force is impressed on the resonant filter, and such shockelectromotive force produces very little disturbance in the resonant circuit The two asymmetric units are poled for one to be effective for excitation of one polarity-and the other to be eifective for excitation of the other polarity;

I shall describe two forms of apparatus embodying my inventiomand shall then point out the novel features thereof-in claims. I

In the accompanying drawings, Fig. 1 is a diagrammatic view showing one: form of apparatus embodying my invention when used with train carried receivingapparatus for a train control system of the code type. Fig. 2 -is a diagrammatic view-showing another form of apparatus embodying my invention when used with train carried receiving apparatus for a train controlsystem .of the code type. Figs. 3 and lare diagrams 7 illustrating shock excitations and resultantoscillations of receiving apparatus heretofore provided for train control systems of the class here involved.

Like reference characters are used in the different views to designate similar parts.

Referring to Fig. 1, the apparatus comprises a receiver R, a control device CO, a filter FT, an amplifier AM and a master relay MR, to-" gether with the necessary sources of power and circuits.

The receiver R consists of two inductors 3 and 4 mounted on a train in inductive relation to the track rails la and lb, respectively, and which rails are included in a track circuit supplied with alternating current coded at one or more predetermined code rates. The trackway apparatus for supplying such current to rails la and lb is not shown, since it may be of any one of several well-known arrangements and forms no part of my present invention. It is sufiicient for a full understanding. ofmy invention to point out that the rails l a and lb are arranged in a track circuit which is supplied with alternating current of a preselected frequency and which current may be codedat any one of a plurality of different preselected code rates. In order to better understand my invention, the alternating current supplied to rails la and lb will be considered as having a frequency of 100 cycles per second and as being coded at the code rate of 180 interruptions per minute to reflect clear traffic conditions. It will be understood, however, that my invention is not limited to the above frequency and code rate. It follows that an alternating electromotive force is induced in inductors 3 and 4 when such alternating current flows in the rails and such received electromotive force is of the frequency'and code of the railcurrent. Furthermore, the rail current and in turn the received electromotive force, will have a normal amplitude which falls within limits pre determined for'the control system.

Inductors 3 and 4 are connected in series to an input circuit which includes a transformer TI and filter FT. Specifically the inductors 3 and 4 are connected to primary winding 5 of transformer TI as will be readily understood by an inspection of Fig. 1, and it follows that an electromotive force corresponding to that picked up by the inductors is created'in secondary winding 6 of'transformer Tl, the electromotive force of secondary winding 6 having a peak value which falls within given limits predetermined for the system.

Filter FT comprises condensers Cl and C2 and a transformer T2, condenser C2 being connected across secondary winding 8 of transformer T2 and condenser Cl being connected in series with primary winding 1 of transformer T2 to a secondary winding 6 of transformer Tl, by a circuit connection which forms a part of the input circuit and in which circuit connection the control device CO is interposed.

Control device CO comprises two asymmetric units Al and A2 and two resistors RI and R2, units Al and A2 being connected in series across resistors El and R2 in series. The asymmetric units-Al and A2 are disposed with their low resistance, that is, their forward direction, as indicated by arrows placed thereon. These asymmetric units may take different forms and may be, for example, copper oxide rectifier elements assembled in the usual manner except for the fact that the contact plates at each end and at the mid point are extended to form external circuit terminals and as will appear as the specification progresses, these contact plates are included in associated circuits to provide a check against an open circuit in the connections to the asymmetric units.

The circuit connection between transformer Tl and filter FT can be traced from the lefthand terminal, as viewed in Fig. 1, of secondary winding '6 of transformer Tl through wire 9, mid terminal ll] of resistors RI and R2 of the device CO, wire ll, condenser Cl, primary winding 1 of transformer T2, wire l2, mid contact plate l3 of units Al and A2 of the device CO, and wire l4 to the right-hand terminal of secondary winding 6. It is to be noted that control device CO provides two paths across this portion of the input circuit, one path extending from mid terminal I!) connected to wires 9 and H of one side of the input circuit, through resistor R2 and asymmetric unit A2 in its forward direction to mid contact plate 13 connected to wires l2 and I4 of the other side of the in put circuit. The second path extends from mid contact plate l3 through asymmetric unit Al 11 its forward direction and resistor Rl to mid terminal Ill. The function of the control device CO will be made clear presently. The'input circuit is connected to the amplifier AM which in Fig. 1 comprises two stages including electron tubes l5 and I6, respectively. Each tube l5 and I8 is provided with a plate, a control grid and a cathode or filament and is arranged for operation by current supplied from the usual train carried 32 volt source of direct current whose terminals are shown at B32 and C. The 32 volts are converted to 300 volts for use with the plate circuits of the tubes of the amplifier by a motor generator MG whose motor I! is connected to terminals B32 and C and whose generator I8 is provided with terminals B300 and N300 from which direct current of 300 volts is obtained, the negative terminal N300 of generator l8 being connected to terminal C of the current source because this terminal serves as a common terminal. I

Control grid 23 and filament 20 of tube l5 are connected to the output side of filter FT by a circuit that can be traced from control grid 23 through secondary winding 8 and condenser C2 in multiple, wire 28, contact plate 22, asymmetric units Al and A2 in their forward directions to contact plate 2| and thence to filament 20.

Hence receiver R is coupled to the control grid of tube l5 through the input circuit including transformer TI and filter F'I. Filter FT is proportioned to tune the input circuit to resonance at the frequency of the alternating track circuit current, that is, in the case here assumed, to resonance at cycles per second.

The filaments of tubes l5 and I6 are connected in series with control device CO to the 32 volt source of current, the circuit extending from terminal B32 through resistor 34, filamentsv l9 and 20 of tubes l6 and I5, respectively, control device CO and to terminal C. The asymmetric units Al and A2 are poled to block the flow of filament current and thus the filament current flows through contact plate 2|, resistors RI and R2 in series and contact plate 22, and creates a voltage drop across each resistor. Preferably, the two resistors RI and R2 are alike and the voltages across the two are substantially equal. It is to be observed that the top terminal of re- .515501 RI is positive with respect to the mid terminal I and the mid terminal III is positive with respect to the lower terminal of resistor R2.

These voltages across resistors RI and R2 serve as bias voltages for asymmetric units AI and A2. That is, the asymmetric unit AI as disposed in its circuit path across the input circuit as ex plained hereinbefore, is biased by the voltage drop in resistor RI, and asymmetric unit A2 as disposed in its circuit path across the input circuit is biased by the voltage drop of resistor R2. For example, the half cycle of the alternating electromotive force created in secondary winding 6, that causes the left-hand terminal of the winding to be positive, is opposed in flowing through the path extending from mid terminal I0 through resistor R2 and unit A2 in its forward direction to contact plate I3 andwire I4 to the left-hand terminal of winding 6 by the direct voltage drop created in resistor R2 by the filament current. Similarly, the half cycle of the alternating electromotive force that causes the right-hand terminal of winding 6 to be positive, is opposed in flowing through the path extending from contact plate I3 through unit AI in its forward direction and resistor RI to mid terminal II) by the direct voltage drop of resistor RI created by the filament current. That is to say, asymmetric units AI and A2 are provided with what I shall call a negative bias voltage due to the voltage drop of the resistors RI and R2, respectively.

It is to be seen, therefore, that receiver R is connected to the control grid of the first stage tube of the amplifier AM by an input circuit which includes filter FT, and the control device C0 is connected to the input circuit in such a manner as to form two biased shunt paths across the circuit ahead of the filter. Furthermore, in the grid circuit for tube IS, the direct voltage drop across resistors RI and R2 of control device CO serves as a grid bias voltage for that tube.

Plate 24 of tube I is connected to terminal B300 through primary winding 25 of a coupling transformer T3, and since filament 20 of tube I5 is connected to terminal C the tube is provided with a plate circuit in which there appears in amplified form the coded alternating electromotive force applied to the grid of tube I5 through the input circuit. The transformer T3 serves to couple the plate circuit of tube I5 to the grid circuit of the second stage tube I6, grid 26 and filament I9 of tube I6 being connected across secondary winding 21 of transformer T3. The plate 29 of tube I6 is connected to terminal B300 through primary winding 30 of an output transformer T4, a by-pass condenser 3| being connected across winding 30. Secondary winding 32 of transformer T4 is connected to code following master relay MR. Relay MR is preferably of the stick polar type. Consequently at the beginning of each on code period of rail current and in turn at the beginning of each on period of the electromotive force picked up by inductors 3 and 4 and applied to the amplifier through the input circuit, the direct current component of the plate circuit current of tube I6 is varied in one sense due to the amplifying action of tubes I5 and I6 and an electromotive force of a given polarity is induced in secondary winding 32 of transformer T4 to operate relay MR to a corresponding position. Then at the end of each on code period of the rail current, and in turn at the end of each on period of the electromotive force induced in inductors 3 and 4, the'direct current componentof the plate circuit current of tube I6 is varied in the opposite sense and an electromotive force of a polarity opposite to that of said given polarity is induced in secondary winding 32 to operate master relay MR to its other position. Relay MR controls through its contact member 33 train controlling devices, such train controlling devices being governed according to the code rate at which member 33 is operated but these devices are omitted fromthe drawings for the sake of simplicity since they would be of standard arrangement and form 11 part of my present invention The control device C0 is proportioned for the bias voltage provided for units AI and A2 due to the voltage drop at resistors RI and R2 as explained hereinbefore, to be of a value slightly greater than the peak value of the normal alternating electromotive force appearing across secondary winding 6 of transformer TI due to the electromotive force picked up by inductors 3 and 4 in respons to the normal value of the track circuit current. Consequently, under normal condition, with no shock excitation present, the alternating electromotive force is passed by filter FT and applied to the amplifier with little attenuation, the control device CO not affecting the electromotive force because the negative bias voltage created by resistors RI and R2 serves to prevent the flow of current through the units AI and A2 in their forward directions.

Referring now to Fig. 3, the top graphs represent two time spaced electromotive forces created in the train carried inductors due to shock excitation. That is, a shock excitation may create .a half-wave electromotive force of either posi tive or-ne'gative polarity. Such a shock electromotive force when applied to the resonant input circuit of receiving apparatus as heretofore provided creates a group'of oscillations as illustrated in the lower graphs of Fig. 3. Such a group of oscillations when amplified may result in an effective energization of the master relay. Assuming the inductors 3 and 4 of Fig. l are shock excited and an electromotive force of relatively high peak voltage is created therein, the control device CO functions to shunt and reduce the higher values of this shock voltage. For example,'if the wave is one that causes the left-hand terminal of secondary winding 5 to be positive, the higher values of the Wave are shunted due to'current flowing through resistor R2 in opposition to the normal voltage drop of'resistor R2, asymmetric unit A2 in its forward direction and back to the other terminal of winding '6. Similarly, if the wave is one that causes the right-hand terminal of winding 6 to be positive, the higher values of the wave are shunted due to current flowing through resistor R1 in opposition to its normal voltage drop and asymmetric unit AI in its forward direction and back to the left-hand terminal of winding 8. That is to say, all values of the shock wave above the predetermined normal peak value of the cycle electromotive force are shunted through the asymmetric unit of the control device. With the shock wave thus reduced to leave only the lower values of the wave to be applied to the filter. the oscillations set up are too small to cause an effective energization of the master relay. This suppressing action of the control device is brought about by the fact that the impedance of the asymmetric units. when they are conductive, is very much less than the impedance of th circuit from the secondary winding 6 to the filter and most of the voltage of the wave is consumed by winding 6 dueto the current flowing through the asymmetric unit. In some cases, the shock excitation may cause a full cycle. wave, as illustrated in the upper graph of Fig. 4. .Such wave would in apparatus heretofore provided create oscillations similar to that illustrated by the lower graph of Fig. 4. In this case the control device C of Fig. 1 serves to reduce the higher values of each half cycle of the wave because one asymmetric unit is poled to pass one half cycle and the other asymmetric unit is poled to pass the other half cycle.

It is to be observed that in the event the alternating rail current becomes of an abnormal high amplitude and the electromotive force picked up by the inductors is correspondingly high. and above the normal predetermined value, the higher values of this abnormal electromotive force will be shunted by the control device C0 but with no detrimental effect on the normal operation of the apparatus because energy of normal value will be passed to the amplifier.

Referring to Fig. 2, the apparatus is the same as in Fig. 1, except the control device 00 is replaced by a control device COI, and which latter device includes a duodiode tube DT and a resistor R3. Tube DT is provided with a heater or filament 35, two anodes 36 and 31 and two cathodes 38 and 39; anode 36 and cathode 38 formingone diode and anode 31 and cathode 39 forming a second diode. Filament 35 and resistor R3 in series are interposed in the filament circuit of tubes I5 and IS in a manner similar to resistors R2 and RI of Fig. 1. The voltage drop through resistor R3 due to the filament current serves to provide a bias voltage for the diode 31-39 and the voltage drop through filament 35 serves to provide a bias voltage for diode 36-38. In Fig. 2, secondary winding 6 of transformer TI is connected to primary winding 1 of transformer T2 of the filter through wire 40; mid terminal 4| between resistor R3 and filament 35. wire 42, condenser Cl, primary winding 1 and wire 43 to the other terminal of winding 6. 'Control device COI provides two shunt paths acrossthis portion of the input circuit. One path extends from mid terminal 4| through'filament 35, wire 44 and diode 36-38 in its low resistance direction to wire 43. The second path extends from wire 43 through diode 3139 in its low resistance direction, wire 45 and resistor R3 to mid terminal 4|. The direct voltage drop of filament 35 opposes the fiow of current through thefirst path in response to the alternating electromotive force of secondary winding 6, and the direct voltage drop of resistor R3 opposes the flow of current through the second path in response to the alternating electromotive force of secondary winding 6. That is, diode 3638 is provided with a negative bias voltage equal to the voltage drop of filament 35 and diode 3'l39 is provided with a negative bia voltage equal to the voltage drop of resistor R3. The remaining portion of the apparatus of Fig. 2 is the same as that of Fig. 1 and the description of the apparatus need'not be repeated.

Filament 35 and resistor R3 are proportioned for each to provide a voltage drop slightly greater than the" peak value of the normal alternatin electromotive force created in secondary winding 6 due'to the alternating rail current. Hencelwhen an alternating electromotive force is picked up by inductors 3' and 40f Fig. 2 due to the usual track circuit current, the corresponding electromotive forcecreated in secondary winding 6 is transferred and applied through filter FT to the amplifier, the control device COI not affecting the electromotive force because of the bias placed on the diodes. If inductors 3 and 4 of Fig. 2 are shock excited and the wave is one that causes the left-hand terminal of secondary winding 6 to be positive, the higher values of the wave cause current to flow through the path including filament 35 and diode 36-38 in its forward direction, and if the wave is one that causes the right-hand terminal of winding 6 to be positive, the higher values of the wave cause current to fiowthrough diode 31-39 in its forward direction, and resistor R3, and this shunting action caused by the control device COI serves to reduce the shock wave to such a low value that the 0s cillations produced in the filter are not of sufllcicnt magnitude to cause an effective operation of the master relay. That is to say, the control fevice COI functions to reduce and suppress shock excitation in substantially the same manner as explained for control device C0 of Fig. 1. i

It should be pointed out that the control devices CO and COI can be used with a single stage amplifier or an amplifier with more than two stages if desired. Also, they can be used with a low voltage amplifier, that is, an amplifier arranged to operate on the 32 volts of the usual train carried source without voltage conversion. Again, it is to be observed that the transformer Tl may be omitted and the inductors connected directly to the input side of the filter, the use of transformer Tl serving to insulate the terminal C of the train carried source of current from the inductors to avoid possible ground conditions of the circuit.

Apparatus embodying my invention has the advantage that train carried train controlling devices are substantially free from being falsely operated due to shock excitation caused by magnetzed wheels, magnetized rail spots, propulsion current, loose receiver and similar conditions.

Although I have herein shown and described only two forms of receiving apparatus for train control systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit an. scope of my invention.

Having thus described my invention, what I claim is:

1. In train control apparatus including an electron tube amplifier and a receiver mounted on a train in inductive relation to the track rails to receive an electromotive force in response to an alternating track circuit current, the combination comprising, a filter including a transformer having independent primary and secondary windings and a condenser and said filter tuned to current and cause such current to flow through said resistors to create a voltage drop across said resistors, an input circuit to connect said receiver to said primary winding of said'filter transformer, said control device having a mid terminal of its resistors connected" to one side of said input circuit and a mid contact plate of its asymmetric units connected to the other side of the input circuit to reduce excitation waves created in said receiver in excess to the voltage drop across each resistor as created by the filament current, and other circuit means including said control device to connect said secondary windings of said filter transformer to a control grid and cathode of said tube to apply to said tube said electromotive force as passed by said filter with the tube provided with a grid bias voltage due to said voltage drop of said resistors.

2. In train control apparatus including an electron tube amplifier and a receiver mounted on a train in inductive relation to the track rails to receive an electromotive force in response to an alternating track circuit current, the combi nation comprising, a filter including a transformer having independent primary and secondary windings and a condenser and said filter tuned to resonance at the frequency of said alternating track circuit current, a control device including two asymmetric units connected in series across two resistors in series; a filament circuit for said amplifier tube and including in series a source of direct current, said filament, a first outside contact plate of said asymmetric units, said resistors in series in multiple with said asymmetric units in series and a second outside contact plate of the asymmetric units; said units poled to block the flow of the filament current to create a voltage drop across said resistors due to the filament current flowing through the resistors, an input circuit including a mid contact plate of said asymmetric units and a mid terminal of said resistors to connect said receiver to said primary winding of said filter transformer to pass said electromotive force to the filter and to reduce shock waves created in said receiver greater than the voltage drop of each resistor, and a grid circuit including said resistors in series and said first outside contact plate to connect said secondary winding of the filter transformer to a control grid and filament of said tube to apply said electromotive force to the tube with a tube grid bias voltage equal to the voltage drop of said resistors.

3. In train control apparatus including an electron tube amplifier and a receiver mounted on a train in inductive relation to the track rails to receive an electromotive force in response to an alternating track circuit current, the combination comprising, a filter including capacitance and a transformer having independent primary and secondary windings and said filter tuned to resonance at the frequency of said alternating current, a control device including a resistor and a duodiode tube having a filament; a filament circuit including in series a source of direct current, the filament of said amplifier tube, said resistor and the filament of said duodiode tube; an input circuit to connect said receiver to said primary winding of the filter transformer and said secondary winding of the filter transformer to a control grid and cathode of said amplifier tube, said control device having a mid terminal of said resistor and the filament of the duodiode tube connected to one side of said input circuit ahead of the filter and a common terminal of the anode of one diode and the cathode of the other diode connected to the other side of the input circuit ahead of the filter, and said control device having a connection from the cathode of said one diode to the filament of the amplifier tube and another connection from the anode of said other diode to the filament of the duodiode tube.

4. In train control apparatus including an electron tube amplifier and a pair of inductors mounted on a train in inductive relation to the track rails to receive an electromotive force in response to an alternating track circuit current, the combination comprising, a first transformer having a primary winding connected to said inductors, a filter including a transformer and capacitance and tuned to resonance at the frequency of said alternating current, a control device having two multiple paths one of which paths includes two asymmetric units in series and the other of which paths includes two resistors in series; a filament circuit including in series a source of direct current, a filament of said amplifier tube and said control device; said asymmetric units poled to block the fiow of such filament circuit current to cause the current to flow through said resistors to create a voltage drop across each resistor, a first circuit to connect a secondary winding of said first transformer to a primary winding of said filter transformer, a second circuit to connect a secondary winding of said filter transformer across a control grid and said filament of said amplifier tube, and said control device interposed in said second circuit between said secondary winding of the filter transformer and said tube filament and having a mid terminal of its resistors connected to one side of said first circuit and a mid terminal of its asymmetric units connected to the other side of said first circuit whereby said control device provides a normal grid bias voltage for said tube, reduces shock waves created in said inductors and insulates said inductor from said filament circuit current source.

RALPH K. CROOKS. 

